java - 使用 java swing.image 更改透明度的方法

Question

我用这种方法在框架中绘制图形。

public void paint(Graphics g) {  
    screenImage = createImage(1280, 720); 
    screenGraphic = screenImage.getGraphics(); 
    screenDraw((Graphics2D) screenGraphic); 
    //g.drawImage(BG, 0, 0, null);
    g.drawImage(screenImage, 0, 0, null);
}

public void screenDraw(Graphics2D g) {
    g.drawImage(BG, 0, 0, null); 
    Graphics2D g2 = (Graphics2D)g;
    if(isMainScreen) {
        //g2.setComposite(alphaComposite);
        g2.drawImage(selectedImage, 100, 220, null);
    }
    paintComponents(g);
    this.repaint();  
}

我希望 selectedImage 的透明度为 50% 或其他整数。

private Image selectedImage = new ImageIcon(Main.class.getResource("../pic/something.jpg")).getImage(); 

这是选定的图像，效果很好。

Answer 1

稍微调整一下Image -> BufferedImage代码，然后可以将每个像素设置为透明

Image selectedImage = new ImageIcon([...]).getImage();

//Image -> BufferedImage code
BufferedImage img = new BufferedImage(selectedImage.getWidth(null), selectedImage.getHeight(null), BufferedImage.TYPE_INT_ARGB);
Graphics2D g = img.createGraphics();
g.drawImage(selectedImage, 0, 0, null);
g.dispose();

//set each pixel to be transparent
int transparency = 127; //0-255, 0 is invisible, 255 is opaque
int colorMask = 0x00FFFFFF; //AARRGGBB
int alphaShift = 24;
for(int y = 0; y < img.getHeight(); y++)
    for(int x = 0; x < img.getWidth(); x++)
        img.setRGB(x, y, (img.getRGB(x, y) & colorMask) | (transparency << alphaShift));

//img is now transparent, can replace selectedImage if you want (optional)
selectedImage = img;

如果您使用ImageIO.read(File)而不是 ImageIcon.getImage()，它会直接给你一个 BufferedImage